Formability improvement of austenitic stainless steel by pulsating hydroforming

Pulsating hydroforming process has been verified to prevent the thickness of tube wall thinning and obtain a uniform expansion, which can improve the hydroformability effectively. In the present work, the experimental research was carried out on the influence of pulsating load on the formability of austenitic stainless steels. The results showed that the formability of austenitic stainless steel can be improved by pulsating load in which the effect on formability should be understood from two different aspects of process parameters and material properties. The mechanical property of austenitic stainless steel is obviously improved through loading and unloading mode. The fraction of the strain-induced martensite is increased by pulsating load, which leads to enhance the transformation-induced plasticity effect. Meanwhile, axial feeding process can be motivated during the process of loading and unloading. Consequently applying pulsating load with large amplitude can achieve a more uniform deformation with a more homogeneous thickness distribution beneficial for preventing excessive local thinning and an excellent die filling performance for tube hydroforming.